Changes in cortical microarchitecture are independent of areal bone mineral density in patients with fragility fractures

The effect of brace treatment history on bone density in preoperative patients with adolescent idiopathic scoliosis (AIS) assessed by vertebral bone quality (VBQ) score: a retrospective propensity score-matched analysis

INTRODUCTION

Adolescent idiopathic scoliosis (AIS), a prevalent condition among teenagers, is often accompanied by osteopenia. However, the impact of brace treatment on bone density in AIS patients remains a matter of debate. The Vertebral bone quality (VBQ) score, derived from MRI signal intensity, has been shown to correlate with bone mineral density (BMD). Yet, no studies to date have drawn comparisons between VBQ scores in preoperative AIS patients who had brace treatment history and those who have not received brace treatment.

OBJECTIVE

This study aims to elucidate the influence of brace treatment on bone density in AIS patients using VBQ score.

METHODS

A retrospective analysis was conducted on 243 AIS patients, each with Cobb angles ranging from 50-70°, who had undergone preoperative MRI scans. The patients were segregated into two cohorts: those who received brace treatment (n = 174) and those who did not (n = 69). Through propensity score matching, a total of 53 matched pairs were selected for further analysis. VBQ scores were extracted from T1-weighted MRI scans.

RESULTS

Post-matching, no significant baseline discrepancies were observed between the two groups. Interestingly, brace-treated patients exhibited lower average VBQ scores than their non-brace-treated counterparts (2.43 ± 0.11 vs. 2.55 ± 0.12, p < 0.01), suggesting a higher bone density. Furthermore, a negative correlation was observed between VBQ scores and the duration of brace usage (R2 = 0.3853, p < 0.01).

CONCLUSION

Brace treatment may potentially enhance bone density in AIS patients by mitigating vertebral fat infiltration. The utilization of VBQ scores presents an alternative, potentially robust approach to assessing bone quality.

The petrous bone contains high concentrations of osteocytes: One possible reason why ancient DNA is better preserved in this bone

The characterization of ancient DNA in fossil bones is providing invaluable information on the genetics of past human and other animal populations. These studies have been aided enormously by the discovery that ancient DNA is relatively well preserved in the petrous bone compared to most other bones. The reasons for this better preservation are however not well understood. Here we examine the hypothesis that one reason for better DNA preservation in the petrous bone is that fresh petrous bone contains more DNA than other bones. We therefore determined the concentrations of osteocyte cells occluded inside lacunae within the petrous bone and compared these concentrations to other bones from the domestic pig using high resolution microCT. We show that the concentrations of osteocyte lacunae in the inner layer of the pig petrous bone adjacent to the otic chamber are about three times higher (around 95,000 lacunae per mm3) than in the mastoid of the temporal bone (around 28,000 lacunae per mm3), as well as the cortical bone of the femur (around 27,000 lacunae per mm3). The sizes and shapes of the lacuna in the inner layer of the petrous bone are similar to those in the femur. We also show that the pig petrous bone lacunae do contain osteocytes using a histological stain for DNA. We therefore confirm and significantly expand upon previous observations of osteocytic lacuna concentrations in the petrous bone, supporting the notion that one possible reason for better preservation of ancient DNA in the petrous bone is that this bone initially contains at least three times more DNA than other bones. Thus during diagenesis more DNA is likely to be preserved in the petrous bone compared to other bones.

Micro-CT analysis of the Lisfranc complex reveals higher bone mineral density in dorsal compared to plantar regions

Injuries to the Lisfranc complex may require surgical fixation, the stability of which may be correlated with bone mineral density (BMD). However, there is limited research on regional BMD variations in the Lisfranc complex. This study used quantitative micro-CT to characterize regional BMD in the four bones (medial cuneiform, intermediate cuneiform, first metatarsal, and second metatarsal) of this complex. Twenty-four cadaveric specimens were imaged with a calibration phantom using micro-CT. Each bone was segmented and divided into eight regions based on an anatomical coordinate system. BMD for each octant was calculated using scan-specific calibration equations and average image intensity. Differences between regions were analyzed using ANOVA with post hoc analysis and differences between groups of four octants in each plane were analyzed with t-tests with significance level α = 0.05. The highest density region in the medial cuneiform was the distal-dorsal-lateral and dorsal regions showed significantly higher BMD than plantar regions. The intermediate cuneiform had the highest density in the distal-dorsal-medial region and the dorsal and medial regions had higher BMD than the plantar and lateral regions, respectively. The densest region of the first metatarsal was the distal-dorsal-lateral and distal regions had significantly higher BMD than proximal regions. In the second metatarsal, the distal-dorsal-medial region had the highest density, and the distal, dorsal, and medial regions had significantly higher BMD than the proximal, plantar, and lateral regions, respectively. The predominant finding was a pattern of increased density in the dorsal bone regions, which may be relevant in the surgical management of Lisfranc injuries.

Bone microarchitecture in patients with autoimmune hepatitis

In patients with autoimmune hepatitis (AIH), osteoporosis represents a common extrahepatic complication, which we recently showed by an assessment of areal bone mineral density (aBMD) via dual-energy x-ray absorptiometry (DXA). However, it is well established that bone quality and fracture risk does not solely depend on aBMD, but also on bone microarchitecture. It is currently not known whether AIH patients exhibit a site-specific or compartment-specific deterioration in the skeletal microarchitecture. In order to assess potential geometric, volumetric, and microarchitectural changes, high-resolution peripheral quantitative computed tomography (HR-pQCT) measurements were performed at the distal radius and distal tibia in female patients with AIH (n = 51) and compared to age-matched female healthy controls (n = 32) as well as to female patients with AIH/primary biliary cholangitis (PBC) overlap syndrome (n = 25) and female patients with PBC alone (PBC, n = 36). DXA at the lumbar spine and hip, clinical characteristics, transient elastography (FibroScan) and laboratory analyses were also included in this analysis. AIH patients showed a predominant reduction of cortical thickness (Ct.Th) in the distal radius and tibia compared to healthy controls (p < .0001 and p = .003, respectively). In contrast, trabecular parameters such as bone volume fraction (BV/TV) did not differ significantly at the distal radius (p = .453) or tibia (p = .508). Linear regression models revealed significant negative associations between age and Ct.Th (95% confidence interval [CI], -14 to -5 μm/year, p < .0001), but not between liver stiffness, cumulative prednisolone dose (even after an adjustment for age), or disease duration with bone microarchitecture. The duration of high-dose prednisolone (≥7.5 mg) was negatively associated with trabecular thickness (Tb.Th) at the distal radius. No differences in bone microarchitecture parameters between AIH, AIH/PBC, and PBC could be detected. In conclusion, AIH patients showed a severe age-dependent deterioration of the cortical bone microarchitecture, which is most likely the major contribution to the observed increased fracture risk in these patients. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

High resolution 3D structures of mineralized tissues in health and disease

A thorough knowledge of the structures of healthy mineralized tissues, such as bone or cartilage, is key to understanding the pathological changes occurring during disease. Such knowledge enables the underlying mechanisms that are responsible for pathology to be pinpointed. One high-resolution 3D method in particular - focused ion beam-scanning electron microscopy (FIB-SEM) - has fundamentally changed our understanding of healthy vertebrate mineralized tissues. FIB-SEM can be used to study demineralized matrix, the hydrated components of tissue (including cells) using cryo-fixation and even untreated mineralized tissue. The latter requires minimal sample preparation, making it possible to study enough samples to carry out studies capable of detecting statistically significant differences - a pre-requisite for the study of pathological tissues. Here, we present an imaging and characterization strategy for tissue structures at different length scales, describe new insights obtained on healthy mineralized tissues using FIB-SEM, and suggest future research directions for both healthy and diseased mineralized tissues.

A Narrative Review of Metatarsal Bone Stress Injury in Athletic Populations: Etiology, Biomechanics, and Management

Metatarsal bone stress injuries (BSIs) are common in athletic populations. BSIs are overuse injuries that result from an accumulation of microdamage that exceeds bone remodeling. Risk for metatarsal BSI is multifactorial and includes factors related to anatomy, biology, and biomechanics. In this article, anatomic factors including foot type, metatarsal length, bone density, bone geometry, and intrinsic muscle strength, which each influence how the foot responds to load, are discussed. Biologic factors such as low energy availability and impaired bone metabolism influence the quality of the bone. Finally, the influence of biomechanical loads to bone such as peak forces, load rates, and loading cycles are reviewed. General management of metatarsal BSI is discussed, including acute care, rehabilitation, treatment of refractory metatarsal BSI, and evaluation of healing/return to sport. Finally, we identify future research priorities and emerging treatments for metatarsal BSI.

Cortical parameters predict bone strength at the tibial diaphysis, but are underestimated by HR-pQCT and μCT compared to histomorphometry

Cortical bone and its microstructure are crucial for bone strength, especially at the long bone diaphysis. However, it is still not well‐defined how imaging procedures can be used as predictive tools for mechanical bone properties. This study evaluated the capability of several high‐resolution imaging techniques to capture cortical bone morphology and assessed the correlation with the bone's mechanical properties. The microstructural properties (cortical thickness [Ct.Th], porosity [Ct.Po], area [Ct.Ar]) of 11 female tibial diaphysis (40–90 years) were evaluated by dual‐energy X‐ray absorptiometry (DXA), high‐resolution peripheral‐quantitative‐computed‐tomography (HR‐pQCT), micro‐CT (μCT) and histomorphometry. Stiffness and maximal torque to failure were determined by mechanical testing. T‐Scores determined by DXA ranged from 0.6 to −5.6 and a lower T‐Score was associated with a decrease in Ct.Th (p ≤ 0.001) while the Ct.Po (p ≤ 0.007) increased, and this relationship was independent of the imaging method. With decreasing T‐Score, histology showed an increase in Ct.Po from the endosteal to the periosteal side (p = 0.001) and an exponential increase in the ratio of osteons at rest to those after remodelling. However, compared to histomorphometry, HR‐pQCT and μCT underestimated Ct.Po and Ct.Th. A lower T‐Score was also associated with significantly reduced stiffness (p = 0.031) and maximal torque (p = 0.006). Improving the accuracy of Ct.Po and Ct.Th did not improve prediction of the mechanical properties, which was most closely related to geometry (Ct.Ar). The ex‐vivo evaluation of mechanical properties correlated with all imaging modalities, with Ct.Th and Ct.Po highly correlated with the T‐Score of the tibial diaphysis. Cortical microstructural changes were underestimated with the lower resolution of HR‐pQCT and μCT compared to the histological ‘gold standard’. The increased accuracy did not result in an improved prediction for local bone strength in this study, which however might be related to the limited number of specimens and thus needs to be evaluated in a larger collective.

Impact on bone microarchitecture and failure load in a patient with type I Gaucher disease who switched from Imiglucerase to Eliglustat

Gaucher disease (GD; OMIM 230800) is a lysosomal storage disorder caused by a deficiency in acid beta-glucosidase as a result of mutation in the GBA gene. Type 1 GD (GD1) is the most common form and its clinical manifestations include severe hematological, visceral and bone disease. The goal of disease-modifying treatments for GD1 is to reduce substrate storage and hence toxicity from the disease. The two common therapeutic routes for managing GD1 are enzyme replacement therapy (ERT) and substrate reduction therapy (SRT). These therapies have shown to improve hematological and visceral aspects of the disease. However, quantitative investigations into how these therapies may help prevent or improve the progression of bone disease is limited. This case involves a patient diagnosed with GD1 in childhood, who began ERT in young adulthood. Following over 20 years of treatment with ERT, the patient switched to SRT. This case report examined the novel application of high-resolution peripheral quantitative computed tomography (HR-pQCT) in a patient who switched from ERT to SRT. Using bone microarchitecture measurements from HR-pQCT, we applied finite element analysis techniques to calculate the failure load which estimates the resistance to fracture. Over the course of one year following the switch from ERT to SRT therapy, failure load improved in the patient's lower limb. In conclusion, failure load can be computed in the short term in a patient who made a switch from ERT to SRT. Further exploration of failure load in study design to look at interventions that impact bone quality in GD may be considered.

Th17 cell frequency is associated with low bone mass in primary sclerosing cholangitis

BACKGROUND & AIMS

Osteoporotic fractures are a major cause of morbidity and reduced quality of life in patients with primary sclerosing cholangitis (PSC), a progressive bile duct disease of unknown origin. Although it is generally assumed that this pathology is a consequence of impaired calcium homeostasis and malabsorption, the cellular and molecular causes of PSC-associated osteoporosis are unknown.

METHODS

We determined bone mineral density by dual-X-ray absorptiometry and assessed bone microstructure by high-resolution peripheral quantitative computed tomography in patients with PSC. Laboratory markers of liver and bone metabolism were measured, and liver stiffness was assessed by FibroScan. We determined the frequency of Th17 cells by the ex vivo stimulation of peripheral blood mononuclear cells in a subgroup of 40 patients with PSC. To investigate the potential involvement of IL-17 in PSC-associated bone loss, we analyzed the skeletal phenotype of mice lacking Abcb4 and/or Il-17.

RESULTS

Unlike in patients with primary biliary cholangitis, bone loss in patients with PSC was not associated with disease duration or liver fibrosis. However, we observed a significant negative correlation between the bone resorption biomarker deoxypyridinoline and bone mineral density in the PSC cohort, indicating increased bone resorption. Importantly, the frequency of Th17 cells in peripheral blood was positively correlated with the urinary deoxypyridinoline level and negatively correlated with bone mass. We observed that Abcb4-deficient mice displayed a low-bone-mass phenotype, which was corrected by an additional Il-17 deficiency or anti-IL-17 treatment, whereas the liver pathology was unaffected.

CONCLUSIONS

Our findings demonstrate that an increased frequency of Th17 cells is associated with bone resorption in PSC. Whether antibody-based IL-17 blockade is beneficial against bone loss in patients with PSC should be addressed in future studies.

LAY SUMMARY

Primary sclerosing cholangitis (PSC) is a cholestatic liver disease characterized by progressive bile duct destruction. One serious complication of PSC is reduced bone mass resulting in increased fracture risk. Herein, we demonstrate that Th17 cells mediate bone loss in PSC by inducing bone resorption, which suggests that antibody-based IL-17 blockade might be beneficial for the treatment of bone loss in affected patients.

Comparison of Bone Microarchitecture Between Adult Osteogenesis Imperfecta and Early-Onset Osteoporosis

Diagnosis and management of adult individuals with low bone mass and increased bone fragility before the age of 50 can be challenging. A number of these patients are diagnosed with mild osteogenesis imperfecta (OI) through detection of COL1A1 or COL1A2 mutations; however, a clinical differentiation from early-onset osteoporosis (EOOP) may be difficult. The purpose of this study was to determine the bone microstructural differences between mild OI and EOOP patients. 29 patients showed mutations in COL1A1 or COL1A2 and were classified as OI. Skeletal assessment included dual-energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT), and bone turnover serum analyses. Bone microstructure of 21/29 OI patients was assessed and compared to 23 age- and sex-matched patients clinically classified EOOP but without mutations in the known disease genes as well as to 20 healthy controls. In the OI patients, we did not observe an age-dependent decrease in DXA Z-scores. HR-pQCT revealed a significant reduction in volumetric BMD and microstructural parameters in the distal radius and tibia in both the OI and EOOP cohorts compared to the healthy controls. When comparing the bone microstructure of OI patients with the EOOP cohort, significant differences were found in terms of bone geometry in the radius, while no significant changes were detected in all other HR-pQCT parameters at the radius and tibia. Taken together, adult mild OI patients demonstrate a predominantly high bone turnover trabecular bone loss syndrome that shows minor microstructural differences compared to EOOP without mutation detection.

Trabecular bone microarchitecture predicts fragility fractures in postmenopausal women on denosumab treatment

BACKGROUND

High-resolution peripheral quantitative computed tomography (HR-pQCT) represents a three-dimensional tool for the screening of osteoporosis patients i.e., regarding fracture risk. The purpose of this study was to determine the baseline and follow-up bone microarchitecture in relation to incident fracture risk in postmenopausal women on denosumab treatment.

METHODS

We have retrospectively evaluated data from 182 postmenopausal women treated with denosumab that underwent an initial HR-pQCT scan before the initiation of the treatment; and at least one second HR-pQCT after 12 months. Women were assigned to two groups based on documented fragility fractures for the following 2.9 ± 1.1 years: fracture (n = 22) and no fracture (n = 160). Baseline parameters from DXA, HR-pQCT and bone turnover were compared between the two groups. Furthermore, ROC and multiple regression analyses of the baseline and follow-up data were performed to evaluate the predictive value regarding incident fractures.

RESULTS

At baseline, trabecular parameters were significantly reduced in the fracture group and showed the best predictive value for new fractures, while DXA results could not predict fractures. A multiple regression model identified BV/TV and age as the best baseline parameters for incident fracture risk. At 12 months, cortical and trabecular parameters increased in the non-fracture group, while no significant increase was noted in the fracture group. However, no significant differences regarding the changes of these parameters could be detected between the non-fracture and fracture cohort.

CONCLUSIONS

Trabecular bone microstructure at baseline is crucial for incident fracture risk in postmenopausal women on denosumab treatment, especially in comparison to DXA values. In this context, the microstructural follow-up results seemed to be of lesser importance regarding fracture risk. The results of this exploratory study should be validated in independent populations.

Prevalence of vitamin D insufficiency and evidence for disease prevention in the older population

The prevalence of vitamin D insufficiency, usually assessed by the analysis of circulating 25-hydroxyvitamin D (25[OH])D), is very high in the aging German population. An important factor that reduces endogenous vitamin D synthesis in older persons is physical inactivity or care-dependency that limits the time spent outside. Additionally, it has been suggested that the age-dependent decline in the glomerular filtration rate is associated with a reduced production of bioactive calcitriol. As this phenomenon is not detectable by the assessment of 25(OH)D, it is necessary to analyze the level of parathyroid hormone as a marker of calcitriol function. Because 25(OH)D levels are highly correlated with an active and healthy life style, data from epidemiological studies are not necessarily suitable to elucidate the role of vitamin D in disease prevention. Recently published meta-analyses of randomized controlled trials (RCTs) showed moderate effects of vitamin D supplementation on fracture risk and found that vitamin D was more effective when administered in combination with calcium. The role of vitamin D in the prevention of falls and frailty remains unclear. Much evidence has demonstrated the beneficial effects of vitamin D on respiratory tract infections and asthma, which are very relevant health issues in the older population. To conclude, vitamin D, particularly combined with calcium, has moderately beneficial effects on the skeletal system and is useful for the prevention of respiratory tract infections.